[Alan Roehrich]

Holes drilled in throttle blades on carburetors are simply to allow the throttle blades to be closed enough at idle to not expose the transition or intermediate circuit, so that excess fuel is not added, and idle mixture can be fully controlled by the idle circuit. It merely allows the carburetor to idle on the idle circuit. The holes are NOT there to expose any of the transition, intermediate, main, or other enrichment circuit to any signal, but rather, in fact, NOT to.


In the case of the Holley carburetors, they are in the secondary plates to allow the secondaries to move some of the air required to make the engine idle. The ALLOWED modifications to the Holley carburetors INCLUDES replacing the secondary metering block or metering plate with a different plate that MAY include an idle circuit. The rule in question was there to prevent, for some reason, the use of four corner idle circuits and adjustability. Currently, when using a secondary metering block or plate that includes and idle circuit, you are supposed to block the idle mixture adjustment screws with plugs.